The valuations for Facebook continue to go up. In 2007 Microsoft took a 1.6% stake in the social network for $240 million. That valued the company at $15 billion, at the time a staggering amount no one really believed was realistic.

Jump forward to 2011 and the 500 million people using Facebook every day is bringing investors out of the woodwork pushing money in the company’s direction. The latest is Goldman Sachs which has just invested $450 million. At the same time Russian investment firm Digital Sky Technologies invested a further $50 million on top of the $500 million it has already invested in Facebook.

While the new capital will be welcomed by Facebook’s management, it also pushes up the value of the company to an all time new high of $50 billion. That in turn has increased Mark Zuckerberg’s expected worth to around $14 billion, almost on a par with Google’s Page and Brin at $15 billion each.

While Zuckerberg has said Facebook going public is a long way off, investments such as this put more pressure on the company to do so. What’s clear though, is Goldman Sachs’ large investment now puts it in a very strong position to handle the public offering when it does eventually happen.

This is a clever investment by Goldman Sachs not only because Facebook is going to continue to grow in value, but because they now have a strong position when the public offering happens. That will generate a lot of additional revenue for the company as well as seeing their Facebook shares grow in value.

Not everything may go Goldman’s way, though. The NYTimes suggests the investment firm may try and offer Facebook investments to its customers through a “special purpose vehicle” which gets around the issue of having to disclose financial results at such a large investment company. The S.E.C. is obviously going to look into that and could block it.

A $50 billion valuation on Facebook is not something I ever thought I’d hear, but then I was surprised when the Microsoft investment valued the company at $15 billion. When Facebook does eventually go public it may shock everyone by either having a share price much higher than expected, or bursting the bubble for all these early investors with a reality check and low price.